Thiamine, also known as vitamin B1, is a water-soluble vitamin that exists in the body as free thiamine and in one of several phosphorylated forms including thiamine monophosphate (ThMP), thiamine pyrophosphate (ThPP), thiamine triphosphate (ThTP), and adenosine thiamine triphosphate (AThTP). In human body, the primary vitamin B1 in serum and plasma is free thiamine while ThPP predominates in cellular components, for example blood cells. ThMP and ThTP only exist in very limited amounts (under detection level) in body fluid. The AThTP was recently discovered in Escherichia coli (Nature Chemical Biology 3, 211-212, 2007). Its existence and significance in human have not been reported at present.
Thiamine and its derivatives play an important role in the metabolism of lipids and carbohydrates. ThPP, also known as thiamine diphosphate (ThDP), is the major biologically active form of thiamine and is a required coenzyme for a number of enzymes involved in carbohydrate metabolism and nervous system function including the biosynthesis of lipids and acetylcholine. Thiamine-requiring enzymes include, for example, pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, branched-chain α-ketoacid dehydrogenase, transketolase, and 2-hydroxyphytaoyl-CoA lyase.
Thiamine in food is easily decomposed by heat and particularly under alkaline conditions. After oral ingestion, thiamine is readily absorbed by both active transportation at low concentrations (<5 mg/dL) and passive diffusion at higher concentration levels. Phosphorylation in the jejunal mucosa produces ThPP.
Thiamine deficiency is frequently caused either by an inadequate intake of thiamine-rich foods (e.g., peas, spinach, liver, beef, and bananas), impaired absorption (genetic), over consumption of thiaminase-rich foods (e.g., raw fish and shellfish) or food high in anti-thiamine factors (e.g., tea and coffee), general malnutrition, or alcoholism. Thiamine deficiency results in a variety of diseases with a myriad of symptoms affecting virtually every system in the body. Beriberi, for example, is a condition induced by thiamine deficiency which is characterized by peripheral neuropathy resulting in abnormal reflexes, diminished sensation, muscle pain and weakness, and seizures. “Wet” beriberi affects the cardiovascular system, with peripheral edema and tachycardia due to congestive heart failure. The cerebral form of the disease may result in Wernicke's encephalopathy, Korsakoff's psychosis, or Wernicke-Korsakoff Syndrome.